🚀 go-pugleaf

In article <1992Aug7.224514.12152@parc.xerox.com>, jellinek@Xerox.com (Herb Jellinek) writes:
> 
(first off, please limit your output to lines of less that 80 characters
if you want all possible people reading it to bother answering) 

The existing ASYNC port on any pc is a darn site cheaper than any SYNC
one you might have to buy, and you won't have software hassles. 

That port can easily go to 57.6kb or 115.2kb ASYNC, and will do so
reliably if you use the National NS-16550-AFN uart in your serial i/o
card. The uart will cost $10 - $15, just DO IT. 

On a DDS-II (aka BDS, or in CA it is called ADN) circuit you normally
only get 56kb sync. There are MANY CSU/DSUs out there that can do ASYNC
as a side benefit, but most stop at 19.2, a few go to 38.4, and even
fewer go to 57.6 (with the async start + stop bits stripped the
remaining real data easily fits on the 56kb sync channel). 

Earlier generations of CSU/DSUs all ran ONLY at whatever line speed you
ordered. Newer ones can often rate adapt to lower speeds from higher
ones. In many areas, a DDS line is the same price regardless of speed,
but to change the speed costs hundreds of dollars or even a whole new
circuit install (try $1000 for both ends of a LOCAL DDS install in NYC).

Getting a CSU/DSU that works at the fastest (56kb or 64kb) rate
available, but that will rate adapt downward and/or convert to async is
the best strategy. 

One company claims to have a 57.6kb async CSU/DSU. The also have a pricy
adapter for any SYNC CSU/DSU to make it run ASYNC at 57.6. In fact their
ASYNC CSU/DSU is really a classic (generations *old*) Case-DATATEL - NOW
known as Dowty - CSU/DSU that they oem and stuff their card into. They
also claim a patent on their strategy - if anyone really cares, I cam
probably dig out the number. 

They want $1500. OUCH!! And that CSU/DSU they oem is old enough so that
it runs at the speed you ordered the line at ONLY. I won't even bother
you with their name. 

One of the highest tech manufacturers is Adtran. You almost never hear
of them because they mostly sell to telcos and OEM customers. Their CSU
II AR does all sort of tricks, even does switched 56 dial backup!, but
only does 19.2 ASYNC rate adapting down from 56 (or from a 19.2 SYNC DSS
line, of course). It does all the lower speeds, 19.2, 38.4, 56, and 64
in sync mode and can support secondary channel for all speeds except
64kb where there is none possible. They support all speeds on v.35 and
rs232 connections. The sec channel has its own rs232 port. This unit
lists at $729. It is a *SUPER* unit.

They have a newer model in the works that has more features but has been
reengineered (a new ASIC cuts out a daughter card), and with competition
out there, may not cost any more than the current model. The new one
definitely does 57.6 ASYNC and does so without any patent violations. 

Their new one is actually in production for some unnamed OEM customer (I
suspect NEC - see below - but am not sure). The version of it with their
own name on it is probably a few months away. Adtran is at 800-726-8663
- so says the back of a manual. 

BAT has some very low cost CSU/DSUs. They have one that does 38.4 async.
If you get discouraged when you first see one, realize that they do work
well and are used in some very reputable networks. I think styling was
not an important issue with them... 

NEC has a new model N6450 (boxed) I6450 (card cage 1 unit per card)
I6452 (2 per card) CSU/DSU that claims 57.6 async. That boxed one has a
list of $995. 1.800.222.4NEC ext 1277. 

At the lower speeds (not 57.6) there are assorted traditional
SYNC<->ASYNC adapters out there. Several brands are all probably made by
RAD, but there are others. This is not the route I personally would go,
but it may be of interest to someone. 

Want an inexpensive termial server that speaks SLIP/TCP-IP/LAT ? Look at
DEC's new DS700. Even in the 16 port version with less than full modem
leads, I think it has more modem lead type functionality than the cisco
MGS box sized Trouters I have seen. The 8 port version has FULL modem
lead control. This DEC box does 57.6 and 115.2kb. That makes it a good
choice for modem connections running 4:1 compression on top of 14.4 or
higher, where 38.4 wastes speed. 115.2 is even fast enough for
compression on top of the coming v.fast modems. 

The 16 port one lists for 3995 I think, but a dealer here in Cambridge
claimed to have some new ones at $2400 (Eli's for those that care). 

If anyone knows of other CSU/DSUs at good prices that do 38.4 or better
57.6, please let me know. 

(no affiliation with any of above)